1 files changed, 56 insertions, 0 deletions
diff --git a/storage/transactional/index.go b/storage/transactional/index.go
new file mode 100644
index 0000000..84e0e2f
--- /dev/null
+++ b/storage/transactional/index.go
@@ -0,0 +1,56 @@
+package transactional
+
+import (
+	"gopkg.in/src-d/go-git.v4/plumbing/format/index"
+	"gopkg.in/src-d/go-git.v4/plumbing/storer"
+)
+
+// IndexStorage implements the storer.IndexStorage for the transactional package.
+type IndexStorage struct {
+	storer.IndexStorer
+	temporal storer.IndexStorer
+
+	set bool
+}
+
+// NewIndexStorage returns a new IndexStorer based on a base storer and a
+// temporal storer.
+func NewIndexStorage(s, temporal storer.IndexStorer) *IndexStorage {
+	return &IndexStorage{
+		IndexStorer: s,
+		temporal:    temporal,
+	}
+}
+
+// SetIndex honors the storer.IndexStorer interface.
+func (s *IndexStorage) SetIndex(idx *index.Index) (err error) {
+	if err := s.temporal.SetIndex(idx); err != nil {
+		return err
+	}
+
+	s.set = true
+	return nil
+}
+
+// Index honors the storer.IndexStorer interface.
+func (s *IndexStorage) Index() (*index.Index, error) {
+	if !s.set {
+		return s.IndexStorer.Index()
+	}
+
+	return s.temporal.Index()
+}
+
+// Commit it copies the index from the temporal storage into the base storage.
+func (s *IndexStorage) Commit() error {
+	if !s.set {
+		return nil
+	}
+
+	idx, err := s.temporal.Index()
+	if err != nil {
+		return err
+	}
+
+	return s.IndexStorer.SetIndex(idx)
+}